In the fields of paints, adhesives, printing inks or the like, a solvent has played an important role. The solvent is basically required to have a high capability of dissolving solutes. In addition, in these fields, the solvent affects largely the wettability, drying property and the like of a coated surface.
As a solvent used together with resins such as cellulose, epoxy, acrylic, vinyl acetate, vinyl chloride, alkyd, and polyester that have been conventionally used so far in the fields of paints, adhesives, printing inks or the like, glycolether cellosolve, particularly cellosolve acetate, has been preferentially used due to the excellent properties thereof. However, in recent years, requirement for the safety of chemical substances has been intensified because of pollution problems and the like. Restriction on the use of cellosolve acetate has been tightened because of its toxicity, and a concentration standard of cellulose acetate for the working environment has been set up under the Industrial Safety and Health Law.
In view of the above circumstances, an alternative solvent that has an adequate capability of dissolving solutes comparable to cellosolve acetate and has no fears for safety issues has been developed actively.
For example, ethyl lactate, propylene glycol monomethylether acetate, methoxypropanol, ethyl β-epoxypropionate, and others have been investigated as a potential candidate for the alternative solvent. However, these are not necessarily satisfactory considering the capability of dissolving solutes, safety issues, odor, handling performance, and others. Among these, ethyl lactate that is approved as a food additive may be considered to be the most preferable in view of safety issues, but ethyl lactate is still not satisfactory in view of the capability of dissolving polymer compounds and various kinds of additives.
Further, from the viewpoint of the capability of dissolving solutes, alkyl esters of β-alkoxypropionic acid such as methyl β-methoxypropionate and ethyl β-ethoxypropionate have been considered to be the most preferable, but these are also not satisfactory in view of the capability of dissolving polymer compounds and various kinds of additives, further in view of volatility after coating.
Besides the fields of applications described above, a solvent has been used for cleaning oils such as cutting oil, working oil, pressing oil, antirust oil, lubricating oil, grease, pitch or the like. In addition, a solvent has been used for cleaning solder flux, ink, liquid crystals, and others. For these cleaning applications, there has been widely used a solvent containing mainly a halogenated solvent such as Freon 113 (1,1,2-trichloro-1,2,2-trichloroethane), methylchloroform (1,1,1-trichloroethane), and trichloroethylene. In particular, Freon 113 has been widely used because Freon 113 is not only non-flammable, less-toxic and excellent in safety, but also hardly corrode metals, plastics, elastomers and others and can selectively dissolve various kinds of stains. However, Freon 113 and methylchloroform destroy the ozone layer in the stratosphere and eventually cause skin cancer, so that the use thereof is rapidly becoming restricted. Trichloroethylene is also suspected to cause cancer and the use thereof is being restricted in view of safety issues.
In view of the foregoing, development of an alternative Freon-based cleaning agent that has cleaning properties that could replace Freon 113 and the like and has no fear of destroying the ozone layer has been carried out actively. For example, Patent Document 1 discloses a solvent containing 1,2-difluoroethane as a main component. Patent Document 2 discloses a mixture of 1,1-dichloro-2,2,2-trifluoroethane and dimethoxybenzene. Patent Document 3 discloses a solvent containing hexafluorobenzene as an essential component. However, these solvents fall short of Freon 113 in terms of the performance. In addition, the use of these halogenated solvents is becoming to be completely restricted due to environmental problems and safety issues.
Patent Document 1: Japanese Patent Laid-Open Publication No. H01-132694
Patent Document 2: Japanese Patent Laid-Open Publication No. H02-178396
Patent Document 3: Japanese Patent Laid-Open Publication No. H03-167298